The File API FileReader object operates the same way in Chrome as it does in FireFox, Opera, or Internet Explorer 10 (Yup, works in IE).
Simple Example
You start by declaring a new instance of the reader:
var reader = new FileReader();
Define your callbacks for its various events:
reader.onloadend = function(){
document.body.style.backgroundImage = "url(" + this.result + ")";
}
And then pass it something to read:
reader.readAsDataURL(file);
Fiddle: http://jsfiddle.net/jonathansampson/K3A9r/
Handling Multiple Files
When you're working with multiple files, things are a bit different. While it's clear we need to cycle over the resulting FileList, we'll also need to use a closure to prevent file data from getting tampered with over numerous iterations:
// Continue only if we have proper support
if ( window.FileReader ) {
// Provide our logic upon the change even of our input
document.getElementById("collection").onchange = function(){
// Couple variables for handling each file
var counter = -1, file;
// Cycle over all files
while ( file = this.files[ ++counter ] ) {
// Create a reader for this particular file
var reader = new FileReader();
// Respond to the onloadend event of the reader
reader.onloadend = (function(file){
return function(){
var image = new Image();
image.height = 100;
image.title = file.name;
image.src = /^image/.test(file.type) ? this.result : "t9QlH.png";
document.body.appendChild( image );
}
})(file);
// Begin reading data for this file
reader.readAsDataURL( file );
}
}
}
Fiddle: http://jsfiddle.net/jonathansampson/jPTV3/
Feature Detection
Although FileReader is available in nearly all modern browsers, you still want to be sure you don't cause any ruckus for users on older browsers. Prior to using the FileReader, be sure to check the window object for its presence:
if ( window.FileReader ) {
// Safe to use FileReader
}
Running Locally, From Chrome
I should note that running this in a file:/// path in Chrome will result in a broken experience. By default, current versions of Chrome don't permit file:/// pages to access other files. You can change this behavior loading Chrome with the --allow-file-access-from-files flag.
![enter image description here]()
Note, this method will only permit file access for files on the instance of the browser it was opened with. If you want this to be the case for all browser instances into the future, you could modify the shortcut from your desktop. Simply right-click the Chrome shortcut, and go to properties. Next, add the flag to the end of the target.
reader.readAsText(file)is an asynchronous operation. You need an event handler to handle the onload event which will contain the resulting text.reader.onload = function(data){console.log(data.target.result);}A loop will not work. – Podvin